As a method for producing a porous apatite material, the foaming method (as described, e.g., in Philips Tech. Rev., vol. 37, p234-236 (1977)) and the thermal decomposition method (as described, e.g., in JP-A-57-4710 and JP-A-58-129087) have been conventionally known. (The term "JP-A" as used herein means an "unexamined published Japanese patent application")
In the foaming method, a foaming agent such as hydrogen peroxide or the like is added to a calcium phosphate slurry, and the slurry is dried and foams so as to produce a porous material. However, the pore diameter and the porosity are difficult to control in this method.
In the thermal decomposition method, thermally decomposable particles such as organic polymer resin particles or the like are mixed with a calcium phosphate slurry, and after molding, the resin particles are burnt out by heating so as to produce a porous material; or a polyurethane foam material is impregnated with a calcium phosphate slurry, and the polyurethane foam material is burnt out by heating so as to produce a porous material. However, toxic gases, which are harmful for environment pollution, are generated upon decomposing the organic polymer resin or the poilyurethane foam material.